Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$125.82	12.671%	$141.7627	$141.76	$141.75	$141.80
Purchase #2	$59.99	8.712%	$65.2163	$65.22	$65.20	$65.20
Purchase #3	$67.42	13.600%	$76.5891	$76.59	$76.60	$76.60
Purchase #4	$102.33	5.362%	$107.8169	$107.82	$107.80	$107.80
Purchase #5	$175.29	5.700%	$185.2815	$185.28	$185.30	$185.30
Purchase #6	$105.71	3.823%	$109.7513	$109.75	$109.75	$109.80
Purchase #7	$124.58	4.380%	$130.0366	$130.04	$130.05	$130.00
7 purchase totals =	$761.14		$816.4544	$816.46	$816.45	$816.50